981  
FXUS02 KWBC 051929  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
328 PM EDT FRI AUG 05 2022  
 
VALID 12Z MON AUG 08 2022 - 12Z FRI AUG 12 2022  
 
...MONSOONAL PATTERN REMAINS ACTIVE ACROSS THE SOUTHWEST WITH  
ADDITIONAL HEAVY RAINFALL LIKELY WHILE THREAT OF HEAVY RAIN  
INCREASES OVER NORTHERN NEW ENGLAND MONDAY TO TUESDAY...  
 
   
..OVERVIEW
 
 
THE OVERALL WEATHER PATTERN ACROSS THE CONTIGUOUS U.S. NEXT WEEK  
WILL LIKELY AMPLIFY INTO A TROUGH-RIDGE-TROUGH PATTERN, AS  
SHORTWAVES COMBINE TO DEEPEN A TROUGH IN THE EAST, A SLOW-MOVING  
UPPER LOW OFF THE WEST COAST LIFTS NORTHEASTWARD INTO THE PACIFIC  
NORTHWEST AROUND WEDNESDAY-THURSDAY, WHILE AN UPPER HIGH NUDGES  
EASTWARD FROM THE CENTRAL ROCKIES INTO THE CENTRAL PLAINS.  
MOISTURE LIFTED AHEAD OF THE EASTERN TROUGH AND ASSOCIATED COLD  
FRONT WILL LIKELY LEAD TO AREAS OF HEAVY RAIN AND THUNDERSTORMS  
MAINLY ACROSS THE MIDWEST TO THE OHIO AND TENNESSEE VALLEYS EARLY  
NEXT WEEK BUT TRAINING ACTIVITIES ALONG A WEST-TO-EAST FRONT COULD  
LEAD TO A FOCUS OF HEAVY RAIN ACROSS NORTHERN NEW ENGLAND MONDAY  
TO TUESDAY. MEANWHILE, PERSISTENT MONSOONAL MOISTURE LOOKS TO  
CONTINUE ACROSS PORTIONS OF THE WEST LEADING TO ADDITIONAL HEAVY  
RAINFALL WITH A GRADUAL NORTHWARD EXPANSION OF THE RAIN TOWARD THE  
NORTHERN ROCKIES AS THE WEEK PROGRESSES.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
ENSEMBLE MEANS FROM THE GEFS, ECMWF, AND CMC THIS MORNING ARE  
QUITE AGREEABLE WITH ONE ANOTHER WITH RESPECT TO THE  
AFOREMENTIONED SYNOPTIC EVOLUTION FOR NEXT WEEK. THE LARGEST  
MODEL SPREAD PERTAINS TO THE TIMING OF THE UPPER LOW OFF THE WEST  
COAST AS IT IS FORECAST TO MOVE INTO THE PACIFIC NORTHWEST LATE  
NEXT WEEK. BOTH THE DETERMINISTIC ECMWF AND GFS INDICATE A FASTER  
LANDFALL OF THE UPPER LOW THAN THEIR ENSEMBLE MEANS. THE CMC WAS  
THE OPPOSITE IN THIS RESPECT (WITH THE DETERMINISTIC SOLUTION  
BEING SLOWER). BY NEXT FRIDAY, THE ECMWF/EC MEAN ARE THE FASTEST  
SOLUTIONS IN TERMS OF TAKING THE UPPER TROUGH AND ASSOCIATED LOW  
PRESSURE SYSTEM WELL INTO CENTRAL CANADA IN CONTRAST WITH THE  
SLOWER SOLUTIONS FROM THE GFS AND CMC AS WELL AS EARLIER ECMWF  
RUNS.  
 
THE WPC MEDIUM-RANGE FORECAST PACKAGE WAS BASED ON 40% FROM THE  
00Z ECMWF/00Z MEAN, 40% FROM THE 06Z GFS/GEFS, AND 20% FROM THE  
00Z CMC/CMC MEAN, TRANSITIONING TO MOSTLY A CONSENSUS OF THE  
ENSEMBLE MEANS BY DAY 7. THE RESULTS SHOW GOOD CONTINUITY WITH  
THE PREVIOUS FORECAST PACKAGE.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
AS THE MEDIUM RANGE PERIOD BEGINS MONDAY, AN AXIS OF LOCALLY HEAVY  
RAIN AND THUNDERSTORMS AHEAD OF A COLD FRONT IS EXPECTED TO  
CONTINUE PUSHING SOUTHEASTWARD FROM ACROSS THE LOWER GREAT LAKES  
AND THE MIDWEST INTO THE OHIO VALLEY. MEANWHILE, AN AXIS OF HEAVY  
RAIN IS POSSIBLE ACROSS NORTHERN NEW ENGLAND MONDAY INTO TUESDAY  
AS A WEST-TO-EAST ORIENTED WAVY FRONT COULD AID CELL TRAINING  
ACTIVITIES. THEREFORE, A SLIGHT RISK HAS BEEN INTRODUCED FOR  
NORTHERN NEW ENGLAND FOR DAY 4 (WHICH MAY EXTEND INTO PART OF DAY  
5). SHOWERS AND STORMS WITH LOCALLY HEAVY RAIN WILL SHIFT  
SOUTHEAST EACH DAY AS THE FRONT PROGRESSES, SLIDING ACROSS THE  
EASTERN SEABOARD AND LOWER OHIO/TENNESSEE VALLEYS/SOUTHERN  
APPALACHIANS TUESDAY-WEDNESDAY. SOME HEAVY RAIN RATES AND AMOUNTS  
COULD LEAD TO POTENTIAL FOR FLASH FLOODING IN THESE AREAS,  
ESPECIALLY OVER SENSITIVE LOCATIONS THAT HAVE RECEIVED ABUNDANT  
RAINFALL RECENTLY, THOUGH SOME WAFFLING IN MODEL GUIDANCE LOWERS  
CONFIDENCE IN THE DETAILS. ACTIVITIES SHOULD BECOME MORE  
SCATTERED AS THEY SETTLE INTO THE SOUTHEAST THURSDAY-FRIDAY WHILE  
COOLER AND DRIER AIR MOVES INTO THE NORTHEAST. MEANWHILE,  
MONSOONAL MOISTURE CONTINUES TO IMPACT THE SOUTHWEST WITH ENHANCED  
RAINFALL. ANOTHER WET DAY IS LIKELY ON MONDAY, WITH SOME  
INDICATIONS OF A FOCUS NEAR THE COLORADO/NEW MEXICO BORDER (WHERE  
CONDITIONS ARE ALREADY QUITE WET) THAT HAS PROMPTED A SLIGHT RISK  
ISSUANCE IN THE EXPERIMENTAL DAY 4 ERO. WHILE RAIN AMOUNTS MAY  
GRADUALLY LESSEN IN THIS AREA AS THE WEEK PROGRESSES, THE MOISTURE  
PLUME IS LIKELY TO EXPAND FARTHER NORTH INTO THE INTERMOUNTAIN  
WEST AND GREAT BASIN WITH SOME LOCALLY HEAVY TOTALS POSSIBLE HERE  
AS WELL.  
 
VERY WARM TO HOT TEMPERATURES AROUND 10-15F ABOVE AVERAGE, THOUGH  
NOT QUITE TO RECORD-BREAKING LEVELS, ARE FORECAST TO SHIFT FROM  
THE NORTHWEST MONDAY INTO THE NORTHERN AND THEN CENTRAL PLAINS AS  
THE WORKWEEK PROGRESSES WITH THE EASTWARD NUDGE OF THE UPPER HIGH.  
FARTHER EAST, SLIGHTLY ABOVE AVERAGE HIGH TEMPERATURES IN THE  
NORTHEAST/MID-ATLANTIC EARLY IN THE WORKWEEK WILL MODERATE TO  
RIGHT AROUND NORMAL BEHIND THE COLD FRONT, WHILE SOME BELOW NORMAL  
HIGHS ARE POSSIBLE IN THE OHIO AND TENNESSEE VALLEYS. GIVEN THE  
RAINFALL AND CLOUDINESS OVER THE SOUTHWEST AND GREAT BASIN, HIGHS  
ARE LIKELY TO BE SEVERAL DEGREES BELOW NORMAL THERE.  
 
KONG/TATE  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF THE GREAT LAKES, OHIO VALLEY, AND  
MIDDLE MISSISSIPPI VALLEY, MON, AUG 8.  
- HEAVY RAIN ACROSS PORTIONS OF NEW ENGLAND, MON, AUG 8.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN  
APPALACHIANS AND THE OHIO AND TENNESSEE VALLEYS, TUE-WED, AUG  
9-AUG 10.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES,  
MON, AUG 8 AND THU-FRI, AUG 11-AUG 12.  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHWEST, MON-FRI, AUG 8-AUG  
12.  
- HEAVY RAIN ACROSS PORTIONS OF THE GREAT BASIN, TUE-FRI, AUG  
9-AUG 12.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST,  
THE OHIO VALLEY, AND THE NORTHERN PLAINS.  
- EXCESSIVE HEAT ACROSS PORTIONS OF NEW ENGLAND AND THE  
MID-ATLANTIC, MON-TUE, AUG 8-AUG 9.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND  
NORTHERN GREAT BASIN, MON-TUE, AUG 8-AUG 9.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE NORTHERN PLAINS, TUE-THU,  
AUG 9-AUG 11.  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE  
AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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